Petrogenesis of Silurian Granitoids in the Western Segment of the North Qilian Accretionary Belt, China: Insights Into the Closure of the Northernmost Branch of the Proto-Tethys Ocean

Weidong He, Yunpeng Dong*, Jiaopeng Sun, Lei He, Zonglin Li, Yukun Qi, Kai Ye, Zhigang Wang, Teng Wang

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The North Qilian Accretionary Belt, situated at the northernmost extent of the Proto-Tethys tectonic domain, preserves key tectonic events such as Proto-Tethys Ocean subduction and accretion. Despite ongoing debates about the closure mechanisms and timing of the North Qilian Ocean, our study presents novel findings on granitoids from the Changma region in the western segment of the North Qilian Accretionary Belt. Zircon U–Pb dating indicates an emplacement age of 436 Ma for the Qingshixia pluton and 425 Ma for the Heixialao pluton. The εHf(t) values of the Qingshixia granodiorite range from +8.25 to +10.89, with TDM2 model ages estimated between 614 and 716 Ma. In contrast, the εHf(t) values of the Heixialao monzogranite range from +1.79 to +4.48, with TDM2 model ages spanning from 1127 to 1291 Ma. The Qingshixia granodiorite displays adakitic traits, characterised by high Sr, low Y, low Yb, and a low K2O/Na2O ratio, whilst the Heixialao monzogranite exhibits peraluminous, high-potassium calc-alkaline features. The low concentrations of Ni and Cr, along with moderate Mg# values, suggest that the Qingshixia granodiorite likely originated from the partial melting of a subducting slab. By comparison with experimental melts, the relatively low Rb/Ba and Rb/Sr ratios and higher zircon saturation temperatures of Heixialao monzogranite suggest that it may have formed from partial melting of the mafic middle and lower crust. Integrating these findings with regional geological features and differences between east and west segments, we propose that the western segment of the North Qilian Ocean basin may have closed during the Late Silurian, contributing to a diachronic closure process from east to west and offering insights into the tectonic evolution of the Proto-Tethys Ocean.

Original languageEnglish
JournalGeological Journal
Volumeonline first
DOIs
Publication statusE-pub ahead of print - 21 Nov 2024

Bibliographical note

Publisher Copyright:
© 2024 John Wiley & Sons Ltd.

Funding

This work is supported by the National Natural Science Foundation of China (grants 42072260 and 42372253), the Youth Innovation Team of Shaanxi Universities, and the Natural Science Basic Research Programme of Shaanxi (program 2021JM-158).

FundersFunder number
National Natural Science Foundation of China
Youth Innovation Team of Shaanxi Universities
Natural Science Basic Research Programme of Shaanxi2021JM-158
Not added42072260
Not added42372253

    Keywords

    • granitoids
    • North Qilian
    • petrogenesis
    • Proto-Tethys
    • Silurian

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